Question

What process is responsible for the change in membrane potential that occurs between point 1 and point 3?

1) Movement of Na⁺ into the cell
2) Movement of Na⁺ out of the cell
3) Movement of K⁺ into the cell
4) Movement of K⁺ out of the cell
5) Activation of the Na⁺-K⁺ pump
6) Inhibition of the Na⁺-K⁺ pump

Answer 1

The change in membrane potential between point 1 and point 3 during an action potential is caused by the movement of K+ out of the cell, leading to repolarization.

Step-by-step explanation:

The process responsible for the change in membrane potential between point 1 and point 3 is the movement of K+ out of the cell. During the action potential, once the threshold of excitation is reached, all Na+ channels open and Na+ rushes into the cell, causing depolarization. Subsequently, Na+ channels close and K+ channels open, allowing K+ to leave the cell. This outflow of K+ causes the repolarization of the membrane, bringing the cell back towards its resting potential. The Na+/K+ pump is later involved in restoring the ion gradients and membrane potential, but the movement of K+ out of the cell is immediately responsible for the repolarization phase during an action potential.